Manufacture of stable colloidal solutions of metals.



BOTHO SGHWERIN, 0F FBANKFORT-ON-THE-MAIN, GERMANY, ASSIGNOR T0 ELEKTBO-OSMOSE A. G. (GRAF SC'HW'ERIN-GESELLSCHAFT),

GERMANY, A CORPORATION- OF FRANKFORT-ON-THE-MAIN,

MANUFACTURE OF STABLE COLLOIDAL SOLUTIONS OF METALS.

No Drawing.

To all whom it may concern Be it known that I, BOTHO Sorrwnnm, a subjectof the German Emporer, and residing at Frankfort-on-the-Main, Germany,have invented certain new and useful Improvements in the Manufacture ofStable Colloidal Solutions of Metals, of which the follon ing is aspecification.

It is known that metal sols can be rendered stable by so-ca-lled organicprotective colloids. Such colloids are gelatin, solutions of albumin orother substances of high molecular weight.

- According to the present invention metal sols can be advantageouslyrendered stable by using soluble silicic acid. Should the method ofproducing the metal sol involve the presence of an electrolyte in thesolution the preparation is preferably purified elec tro-osmotically.

The application of water glass in the preparation of metal sols isknown. The present invention, however, resides in the use of solublesilicic acid which is both chemically andphysically considerablydifferent from water glass. It has been shown that in the presence ofeven only small-proportions of an electrolyte the preparation is notstable. Soluble silicic acid presents a material completely .free fromelectrolyte and renders possible theattainment of a high degree ofstability in the metal $01.

It is particularly advantageous to use hydrazin hydrate for thereduction of the metal salt because the silicic acid sol is in-Specification of Letters Patent.

Patented Dec. 1, 1914 Application filed April 18, 1914. Serial No.332,940.

sensitive toward hydrazin hydrate while it is unfavorably afl'ected byother reducing agents, such as formaldehyde, which have a tendency tochange it into the gel form.

The process may be carried out for example as follows :-A solution ofsilicic acid containing about 2.5 per cent. of the acid is mixed with adiluted solution of a gold or silver salt and the metal is reduced by areducing agent suitable for separating it in the colloidal form. If forinstance hydrazin hydrate is the reducing agent a completely clear brownsilver sol, or deep blue gold sol is obtained.

What I claim is:

1. The manufacture of stable colloidal solutions of metals wherein thesolution is renaiered stable by means of soluble silicic acl 2. Themanufactureof stable colloidal solutions of metals consisting in mixingsilicic acid with a solution of ducing the metal in the presence of thesilicic acid.

3. The manufacture of stable colloidal solutions of metals consistin inmixing silicic acid with a solution of t e metal salt and reducing themetal yvith hydraz'in hydrate.

.In testimony whereof I aflix my signature in presence of two witnesses.

, BOTHO SCHWERIN.

WVitnesses J nan Gaonn, CARL GRUND.

a metal salt and re-

